1. Field of the Invention
This invention relates to a magnetic tape cassette, and more particularly to a magnetic tape cassette which is suitable for use for recording and reproducing a digital signal such as, for example, a PCM signal.
2. Description of the Prior Art
A PCM recording and reproducing apparatus is generally used to convert an analog signal such as an acoustic signal to a digital signal such as a PCM signal to carry out recording reproducing of it with respect to a magnetic tape. One of such PCM recording and reproducing apparatus is adapted to use a rotating head to carry out the recording and reproducing at a high density. A magnetic tape for the PCM recording and reproducing apparatus is typically used in a manner to be successively drawn out from a magnetic tape cassette and subjected to recording and reproducing while being wound on a rotating drum.
A magnetic tape used for the PCM apparatus causes dropout of a reproducing signal when a fingerprint, dust or the like adheres thereto. In order to avoid such a problem, it is required to sealedly enclose a magnetic tape in a magnetic tape cassette when it is not used and define a space in the cassette sufficient to receive a guide of the apparatus in the cassette so as to draw out the tape from the cassette during recording or reproducing operation.
In view of the foregoing, a magnetic tape cassette is proposed which includes includes a slider slidably arranged on an outside of a lower casing member constituting a casing of the cassette together with an upper casing member so that it may be slid in a longitudinal direction of the cassette to selectively close a space defined in the cassette for receiving a guide of a recording and/or reproducing apparatus therein. Also, the cassette includes a front cover or lid which is pivotally moved depending on sliding of the slider to selectively cover a front opening or portion of the cassette. The so-constructed magnetic tape cassette, when it is charged in a recording and/or reproducing apparatus, is so operated that the slider which covers a part of each of a bottom surface and side surfaces of the cassette is slid in a rear direction of the cassette to open the space in the cassette for receiing a guide of the apparatus therein and the front cover is pivotally moved to expose a magnetic tape at the front portion of the cassette. When the cassette is not used, the slider and front cover are so positioned that the magnetic tape may be sealedly received in the cassette.
However, the conventional magnetic tape cassette is deteriorated in its safety during the non-use and its reliability in the operation. More particularly, the conventional cassette, as shown in FIGS. 1A to 1C, includes a casing 20 comprising an upper casing member 22 and a lower casing member 24, and a slider 28 slidably mounted on the lower casing member 24 of the casing 20, wherein an upper half of a rear portion of each side of the cassette is constituted by a part of the upper casing member 22 and its lower half is constituted by a part of each of the slider 28 and the lower casing member 24. Also, in the conventional cassette, in order to prevent the slider 28 from being separated or dislocated from the upper and lower casing members 22, 24 in mounting of the slider 28 on the casing 20, an upper portion 50 of each of sides of the slider is inserted in the casing 20 through a gap defined between the upper casing member 22 and the lower casing member 24 so as to be opposite at an outer surface thereof to an inner surface 52 of each of sides of the upper casing member 22. For this purpose, the upper casing member 22 is so formed that the inner surface 52 of the side of the upper casing member 22 is positioned outwardly from an outer surface 46 of an upper portion of each side of the lower casing member 24 inserted or arranged in the casing 20. Unfortunately, such construction, when the cassette is dropped, for example, by mistake, causes the slider 28 to be deformed due to shock applied thereto as shown in FIG. 1c to lead to dislocation or separation of the slider 28 from the casing 20, resulting in deteriorating safety and reliability of the cassette.